1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor device and, more particularly, to an oxidation process in forming a gate electrode of a semiconductor device.
2. Description of the Related Art
Referring to FIG. 1A, a device isolation region 12 defining an active region and an inactive region is formed on a semiconductor substrate 10. A polysilicon layer 14a, a tungsten silicide layer 14b, and a mask nitride layer 14c are sequentially formed on a gate oxide layer (not shown) on the semiconductor substrate 10.
Using a mask for forming a gate electrode, the mask nitride layer 14c, the tungsten silicide layer 14b, and the polysilicon layer 14a are sequentially etched to form a gate electrode. In order to compensate for damage generated on an upper portion and both sidewalls of the gate electrode 14 and the semiconductor substrate 10 during formation of the gate electrode 14, a first oxide layer 16 is formed on the semiconductor substrate 10 and the gate electrode 14 by a thermal oxidation process.
Referring to FIG. 1B and FIG. 1C, a nitride layer 18 is formed over the entire surface of the semiconductor substrate 10 and the first oxide layer 16. The nitride layer 18 is then etched back to form a nitride layer spacer 18a on sidewalls of the gate electrode 14. In order to compensate for damage generated on the gate oxide layer and the semiconductor substrate 10 during dry etch for forming the nitride layer spacer 18a, a second oxide layer 20 is formed on the semiconductor substrate 10 and the gate electrode 14 by the thermal oxidation process.
Owing to the first oxide layer 16 and the second oxide layer 20, the amount of oxidization of the active region of the semiconductor substrate 10 is increased to expand the volume. Owing to the expansion of the volume, the active region is attacked to generate pit-type defect 22 such as a pit. This may generate the fail, thereby reducing the yield of products.